Delivery valve for engine fuel pump



y 5, 1970 v D. J. WALDMAN 3,510,062

DELIVERY VALVE FOR ENGINE FUEL PUMP Filed Dec. 15, 1967 I N VENTOR.

E1 E DONALD J. WALDMAN AT TORNEYS United States Patent 3 510,062 DELIVERY VALVE FOR ENGINE FUEL PUMP Donald J. Waldman, Peoria, Ill., assignor to Caterpillar Tractor Co., Peoria, 111., a corporation of California Filed Dec. 15, 1967, Ser. No. 690,807 Int. Cl. F02rn 41/16 US. Cl. 239-96 2 Claims ABSTRACT OF THE DISCLOSURE A delivery valve for a fuel pump of a compression ignition engine with a small channel in its valving surface to permit bleed back of pressure and fuel trapped in the housing of the injection valve when both the delivery and injection valves are closed.

Cross reference to related US. patents A currently used type of fuel injector is disclosed in my assignees copending application of John M. Bailey, et al. entitled Fuel Injection Valve, Ser. No. 680,824, filed Nov. 6, 1967.

A fuel pump of the type within which the present invention is described is disclosed in greater detail in my assignees Pat. No. 2,696,786 of K. J. Fleck et al., entitled Fuel Injection Pump Plunger.

The fuel injector shown in the referenced copending patent application is of the inwardly opening type known for the characteristic of trapping fluid in its housing under certain operating conditions. Similar valves of different construction have been provided with bleed-off lines leading to a common line and to the atmosphere to reduce excessive residual pressures in the fuel injector. The use of such bleed-off line results in a bulky valve which is of complex and expensive construction as Well as being otherwise undesirable.

It is therefore a principal object of the present invention to provide very simple and inexpensive means for overcoming the above disadvantages.

It i a further object to provide a delivery valve which permits normal delivery of fuel under pressure to an associated fuel injector and which has bleed-off means for reducing undesirable residual pressures in the injector.

Other objects and advantages of the present invention will be made apparent in the following description having reference to the accompanying drawings wherein:

FIG. 1 is a sectional view of a fuel pump and fuel injector for an internal combustion engine; and

FIG. 2 is an enlarged perspective illustration of a delivery valve within the fuel pump of FIG. 1.

Having reference to FIG. 1, a fuel pump 11 is illustrated for delivering fuel under pressure to a fuel injector 12 by means of an interconnecting line 13. Although the present invention may be employed with any fuel injector susceptible to the problems noted above, the illustrated fuel injector 12 is of a type described in detail in the copending patent application first referenced above. Intermittent flow of fuel under pressure from the fuel pump through the line 13 of the fuel injector passes through a series of grooves 14 formed between the injector case 16 and a sleeve 17 disposed therein which prevent passage of foreign materials. The fuel then passes into a valve chamber 18 which is in communication with a passage 19 and injection orifices 21., according to positioning of a check valve 22. The check valve 22 has a valve head 23 with a spherically shaped end which is urged into closing relation with a seating surface 24 by a spring 25 to block the passage 19. An enlarged cylindrical portion 26 at the upper end of the check valve slides within a collar 27 mounted at the lower end of sleeve 17. The sleeve 17 internally defines a fuel accumu- "'ice lator chamber 28. Leakage of fuel between the collar 27 and cylindrical valve portion 26 tends to equalize fuel pressure between the valve chamber 18 and the accumulator chamber 28. As fuel under pressure enters the valve chamber 18, it acts on the undersurfaces of the valve head 23 urging the check valve upwardly and communicating the fuel to the passage 19 and the orifices 21. Upward motion of the check valve 22 is limited by a stop 29. During this operation of the valve, fuel under pressure in the valve chamber 18 passes between the collar 27 and the cylindrical valve portion 26 into the accumulator chamber 28. As the fuel pressure in the valve chamber 18 is reduced by flow across the valve, the spring 25 again causes the check valve to close. Upon reduction of fuel pressure in valve chamber 18, fuel from the accumulator chamber 28 tends to leak back into the valve chamber 18.

The fuel pump 11 is preferably of a type described in detail in the patent referenced above although the invention is equally adaptable to other types of fuel pumps having a delivery valve similar to that described below. Fuel is delivered to a manifold 31 of the pump 11 by another low pressure pump (not shown). Fuel from the manifold 31 is communicated to a plunger bore 32 by a radial passage 33. A plunger 34 is disposed in the bore 32 for reciprocal pumping motion according to interaction of a spring 36 and a cam 37 upon a follower 38 which is connected to the plunger 34. The plunger 34 is of a type providing a variable pumping stroke in response to rotation of the plunger 34 by a rack bar 39 which engages gear teeth 41 on a quadrant fixed to the follower. A delivery valve 42 is urged downwardly against a seating surface 44 by a spring 43. With the delivery valve in this closed position, it cooperates with the plunger bore 32 and the plunger 34 to form a variable pumping chamber 46. When the cam 37 permits the spring 36 to urge the follower 38 and the plunger 34 to their downward limits, the pumping chamber 46 has a maximum volume and is in communication with the fuel in manifold 31 by the passage 33. In this position, low pressure fuel from the manifold 31 enters the pumping chamber 46. The plunger 34 is then urged upwardly against the force of the spring 36 by rotation of the cam 37 so that it closes off the passage 33. Continued upward motion of the plunger 34 forces fuel in the fuel chamber 46 against the delivery valve 42 so that it rise against its spring 43 and communicates the fuel chamber 46 with a passage 47 and the connecting line 13. Fuel is then driven from the fuel chamber 46 to the injector 12 which operates as described above to inject fuel through the orifices 21 into a combustion chamber of an engine (not shown). When the plunger 34 reaches its uppermost limit, continued rotation of the cam 37 permits the spring 36 to urge the plunger downwardly again so that fuel again enters the pumping chamber 46 through the passage 33 and a new injection cycle is commenced.

During normal engine operation, the accumulator chamber 28 causes residual pressures to appear in the valve chamber 18 of the injector 12 during those portions of the pumping cycle of the fuel pump 11 when the delivery valve 42 is closed by its spring 43. At normal engine speed, the numerous injections or pumping cycles cause the delivery valve 42 to fluctuate between its open and closed positions in a floating manner so that residual pressures in the line 13 and the injector 12 are low enough to permit proper operation of the injector 12. However, under certain conditions such as when the engine is turning at low speeds, for example, during cranking, the delivery valve 42 moves only a short distance from its seat 44 and rapidly returns into closed relation therewith. under this condition, it has been found that interaction between the accumulator chamber 28 and the valve 18 in the fuel injector 12 traps incrementally greater residual pressures in the valve chamber 18 with each of the low speed pumping cycles. The greater residual pressures in the valve chamber 18 also appear in the accumulator chamber 28 because of the leakage therebetween. Thus, the residual pressure in the injector valve, upon being incrementally increased by low speed pumping cycles of the pump 11 causes a hydraulic lock of the check valve 26. This lock results when pressure in the accumulator chamber 28 is sufiicient in combination with force of the spring 25 to prevent pressure in the valve chamber 18 from acting upon the undcrsurfaces of the valve head 23 and opening the check valve 22.

To overcome this problem, the present invention provides a modified delivery value which is best seen in FIG. 2. The delivery valve 42 has a face surface 51 which closes with the seating surface 44 (FIG. 1) when the delivery valve is positioned by the spring 43. A limited passage is formed across the delivery valve assembly to relieve residual pressures in the spool injector when the delivery valve is closed. The limited passage is preferably formed, as at 52, between the face surface 51 of the delivery valve and the seating surface 44 when they are in abutting relation. In the present embodiment, the

limited passage 52 is formed by a channel in the face surface 51 of the delivery valve. The channel is sufiiciently small so that, during the pumping stroke of the plunger 34, it does not interfere with the proper pressure development in the pumping chamber 46 nor does it interfere with the manner in which the delivery valve opens to pass that fuel under pressure from the pumping chamber 46 to the fuel injector by means of the line 13. However, when a situation of the type described above develops Where residual pressure in the injector valve exceeds a suitable level, the channel 52 in the closed delivery valve provides suflicient relief for pressure in the injector valve by permitting it to flow back into the pumping chamber 4 46 of the fuel pump 11. Thus, the present invention provides very simple means for relieving residual pressures in the fuel injector without interfering with normal operation of the fuel pump in combination with the ejector.

I claim:

1. A fuel pump in combination with a fuel injector of the inwardly opening type and including a fuel accumulator chamber, the fuel pump being effective for providing fuel under pressure from a fuel source to the fuel injector and comprising a delivery valve assembly comprising a valve and valve seat in the fuel pump having face surfaces normally in abutting relation which open to permit flow of fuel under pressure to the fuel injector, the facing surfaces of the valve and valve seat defining a limited passage when in abutting relation, the passage permitting limited reverse flow of fuel from the injector and reducing residual pressure in the fuel injector.

2. The fuel pump of claim 1 wherein said valve is normally urged against the valve seat by a spring, the valve being intermittently urged into open relation with the valve seat by pressure developed in the pump, said limited passage being a small channel formed in said valve face.

References Cited UNITED STATES PATENTS 2,696,786 12/1954 Fleck et al. l034l 2,729,169 1/1956 Nichols 103-41 2,788,246 4/1957 Nichols 239-96 2,797,644 7/1957 Hogeman l03-4l 2,843,045 7/1958 Mashinter l0341 2,888,876 6/1959 Nichols 103-41 EVERETT W. KIRBY, Primary Examiner US. Cl. X.R.

Disclaimer 3,510,062.D0na1d J. Waldman, Peoria, 111. DELIVERY VALVE FOR EN- GINE FUEL PUMP. Patent dated May 5, 1970. Disclaimer filed Dec. 1, 1983, by the assignee, Caterpillar Tractor Co.

Hereby enters this disclaimer to claims 1 and 2 of said patent.

[Official Gazette January 29. 1985.] 

